According to the National Gardening Association, I have gardened my entire life within a single hardiness zone: 8B (Northern California Coastal & Inland Valleys — minus the inland valleys in my case). In fact, I’ve gardened my entire life within a 35 mile radius of the house where I grew up. This is great in some ways. It has made me a much better gardener within my specific region (what I like to call the nor-cal fog zone, where the temperature sits at right around 55 degrees all year round). And I do love the plants I can grow here: tree ferns and split-leaf philodendrons and bamboo and of course all kinds of cool-weather, low-chill and short season fruits and vegetables. I even managed tomatoes 10 blocks from the foggy beach.
This spring, however, I will be packing up my trowel and moving to a climate so different that I don’t even know where to begin my garden planning. For starters, it snows. I haven’t lived somewhere that snowed since I was 6 1/2 years old. And in the summer the heat — a very, very dry heat — can bake the paint right off the house. And did I mention the altitude? Yeah, I’m way out of my depth on this one. But gardeners, we garden. We don’t know what else to do.
So while most well-seasoned southwest gardeners are probably starting seeds, I will be studying. Luckily I have friends out there who can help me understand this strange new/old world.
And even though my new garden may be temporary, I will give it all the green thumb I have. And then some.
Different plants like different climates. Artichokes like mild weather year round. Okra loves heat and humidity. Apples and plums need a certain number of hours of winter chill to fruit well. To help gardeners know which plants perform best in which areas, the USDA created a map of climate zones, assigning each zone a number. Once you know the number for your area, all you need to do is look for that same number on the label when you shop for plants.
Unfortunately, these zone maps aren’t any guarantee that the plant you choose is actually suited to your area for a couple of reasons:
- It doesn’t account for microclimates—variations from the standard climate of the area caused by terrain, construction, vegetation and other variables. Concrete, for example, collects and retains heat, raising the ambient temperature of the surrounding area, while dense trees keep the ground cooler than usual by preventing sunlight from reaching the ground. Microclimates can even vary within a single yard. A sunny wall in an enclosed backyard can be almost a full number higher than a shady, open area at the front of the house.
- It focuses on lows and largely ignores highs. Just because a plant can’t take freezing weather doesn’t mean it can handle scorching heat. Take for example the artichoke, mentioned earlier. It loves the temperate Northern California coastal marine zone for its fog and even, year-round 50-60 degree temperatures but may not be happy at all in Austin Texas or the Florida panhandle (all zone 8b).
- Climates change. The current map, which was last updated in 1990, no longer accurately reflects the current climate trends. Thankfully, they are currently in the process of updating the map, but that won’t really help the plants you already have in place.
One other thing to consider, plenty of plants, given the right placement and attention, can survive outside their zone. The trick is make sure all of their other needs (sun, water, etc.) are being met and that you’ve placed them in an area of the yard with a microclimate that comes as close as possibly to their preferred zone.
Find Your Zone
NOTE: If you live in the Western United States, check out the Sunset Western Garden Book which has its own zone system designed to account for the extremely varied climates of this area.